#7 misfire? help
Thread Starter
TECH Enthusiast
Joined: Feb 2002
Posts: 551
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From: chicago
#7 misfire? help I am completely lost on this one. 2001 Tahoe 5.3L. I run a figure 8 race with it. Number 7 cylinder is dead. header pipe is cold. I have pulled the plug and replaced it. swapped plug wires coil and injector. Still missing. Checked for spark have tons. checked for injector pulse good. Fuel pressure is at close to 60psi. 175psi compression. Rockers look great push rods are straight. .Pulled the head. valve seals great lifter appears fine compared to the #5 lifter. put the fuel rail back on the truck wired up the injectors. Cranking it the 1st pulse all the injectors fire good and then they tapper off while cranking. Number 7 seems to fire less after the initial cranking. Anyone had a lifter pump up and hold the valve open? any other Ideas?
Do you get any codes? Have you scanned or data logged it?
I had a similar problem and the PCM was bad. For whatever reason a daily driven factory car with no mods dropped #5 cylinder and intermittently wouldn't fire that coil. I could see the misfire code and watch it on the logs. I swapped in a spare PCM I had and all has been well for thousands of miles.
I had a similar problem and the PCM was bad. For whatever reason a daily driven factory car with no mods dropped #5 cylinder and intermittently wouldn't fire that coil. I could see the misfire code and watch it on the logs. I swapped in a spare PCM I had and all has been well for thousands of miles.
Thread Starter
TECH Enthusiast
Joined: Feb 2002
Posts: 551
Likes: 0
From: chicago
I get a p0300 code. the truck has a master kill switch and it loses memory when it is turned off. Like disconnecting the battery. It is a dead miss and it has spark through the wire to the plug and through the plug. Like the injector isn't firing. I switched it with a know good injector. Still nothing. I haven't data logged it. I only have a 2004 PCM and it is different. So no luck there.
